1. Field of the Invention
This invention relates to an operator-independent device for detecting in vivo, determining, and displaying the mass or volume of a body part, particularly the prostate gland.
2. Description of the Prior Art
The disclosure herein is focused on the prostate for description purposes only, however there are many instances in which knowledge of the mass or volume of a body part is material to carrying out certain diagnoses. Such body parts in which the invention may be used diagnostically include, ovaries, testes, kidneys, etcetera.
Prostate cancer is the second leading cause of male cancer deaths in the United States. It is estimated that 132,000 men are diagnosed with this disease annually. It is further estimated that 34,000 die of this disease annually.
Currently, there exist methods for routine screening of prostate cancer. Such methods include the digital rectal exam, the trans-rectal ultrasound exam, and the prostate-specific antigen blood test. These exams are inadequate, alone or in combination, for specific and sensitive detection of early stage prostate cancer.
Digital rectal exams alone, are very subjective, nonsensitive and nonspecific, as often the location of the tumor precludes tactile detection. Moreover, such exams are not effective in determining prostate cancer in its early stages. Trans-rectal ultrasound exams share the same problems as digital rectal exams, while requiring considerable operator skill. Furthermore, ultrasound equipment is costly, and the time required for the patient to undergo the examination is usually lengthy.
The prostate specific antigen test is often used in conjunction with the digital rectal exam, and is gaining acceptance in the medical community. However, the prostate specific antigen test has a very high false positive rate, as studies have shown that over 30% of men with a positive reading are estimated to not have prostate cancer. Moreover, this test is also believed to have a high false negative rate, as studies have shown that in instances of prostate cancer 20% to 40% of men with cancer may have a negative reading. Such false positive readings have led many men to undergo unnecessary biopsies, and such false negative readings have led many men to falsely believe that they are healthy.
Recent research has demonstrated that if the prostate specific blood antigen reading is divided by the volume of the prostate, the false positive rate is reduced to approximately 20% and the false negative rate is similarly reduced to approximately 10%. The rationale for such reduction is that the prostate specific antigen is produced by both normal glandular and cancerous prostatic tissue, so that an enlarged prostate will produce an elevated antigen regardless of whether or not cancerous nodules exist. In order to carry out such a test for routine screening of prostate cancer, a fast, inexpensive, reliable, repeatable, operator-independent, and easily manipulable device, is required to detect the volume of the prostate.
In vivo determinations of the mass of a solid body part do not currently exist in the prior art. There are devices in existence which may be employed to determine the volume of a solid body part, however, many of such devices employ ultrasound. Ultrasonic devices have many disadvantages associated therewith, namely the requirement of image formulation prior to being able to determine the volume, and the fact that such volumetric determinations are operator dependent. Examples of such devices are those disclosed in U.S. Pat. No. 4,100,916 and 4,341,120. With each of these devices, an experienced operator must visually identify the boundaries of the prostate and mark such on a computer screen. Radiologists or other experts are often the only medical personnel who possess the ability to interpret such boundaries. Moreover, interpretation is often difficult, as the operator is required to determine the volume of an area in question based on a reconstructed image thereof. Such devices lend to an increased likelihood of operator error, while lengthening the amount of time required for the exam.
Also in existence, are devices which carry out operator independent volumetric determinations, however these devices are only applicable for hollow or liquid filled chambers, and most devices rely on imaging or the knowledge of tissue boundaries or hypothetical shape assumptions. Additionally, many of such prior art devices lack speed in arriving at such determinations. An example of such a device is disclosed in U.S. Pat. No. 4,926,871, which allows an operator to independently effectuate volumetric determinations, however calculations are performed on a fluid filled bladder and are based on the distance between the front and rear boundaries of the area in question, thus requiring a border detection scheme. Moreover, such a device is ultrasonic and requires an image, thereby enhancing the degree of error associated with the interpretation and reconstruction into an assumed shape. Another operator independent device for measuring the volume of an area in question is disclosed in U.S. Pat. No. 3,310,049 which applies primarily to open chambers, particularly the heart. None of the aforementioned devices are useful in identifying an unknown solid tissue mass directly and providing a numerical output. Additionally, none of the prior art carries out a volumetric determination absent the use of ultrasound and image reconstruction and manipulation.
Additionally lacking in the prior art is a device capable of combining operator independent mass or volumetric determination of the prostate, while enabling the operator to carry out a digital rectal exam. In existence are devices capable of being mounted to the operator's finger so as to enable him to locate an area of suspected a tumor. One such device is disclosed in U.S. Pat. No. 4,250,894. Transducers adjacently disposed on a glove provide determinations as to tumor locations by the differences in voltages on the outputs thereof. However, the placement of the transducers preclude the operator from tactile sensation and no determinations regarding the area in question are made, other than the location of the tumor. Similarly, in U.S. Pat. No. 5,012,817, a finger mounted pressure sensitive transducer enables the detection of the location of a sensitive area on the patient's body. However, this device only determines the pressure applied in response to the pain felt by the patient and provides no data with respect to the parameters of the area in question. In U.S. Pat. No. 4,543,386 an ultrasonic transducer adapted to encompass the operator's finger, enables the operator to obtain a scan of a body cavity. Likewise, U.S. Pat. No. 5,152,293 discloses a similar finger mounted imaging device. However, both devices comprise transducers which are placed completely underneath the fleshy part of the operator's finger, thereby prohibiting the operator from making a tactile determination of the area in question. In U.S. Pat. No. 5,088,500, a finger mounted device enables tactile determination to be carried out, however, this device employs the use of ultrasound which is image based, operator dependent, costly, and entails a lengthy procedure for the patient. Moreover, this device only provides images to the operator, as opposed to numerical determinations.
It is evident that none of the aforementioned prior art devices enable automatic mass or volumetric determinations of a solid body part to be carried out. Moreover, none of the aforementioned devices further enable the operator to make tactile determinations with respect to the area in question while obtaining such automatic mass or volume determinations.